Python List

The Python List is one of the most useful sequence in real-time. A list is a sequence of multiple values in an ordered sequence.

Unlike Python Strings, List allow us to store different types of data such as integer, float, string etc.

List_Name = [] is an empty list that contains no values.
Integer_List = [1, 2, 3, 4, 5] is an integer list that contains five integer values.
String_List = [‘apple’, ‘Orange’, ‘Grape’, ‘Mango’] is a string list that contains four string values.
Mixed_List = [‘apple’, 2, 3.50, ‘Mango’] is a mixed list that contains one integer, one float and two integer values.

Accessing Python List items

We can access the elements in a Python List using indexes. Using index we can access or alter/change each and every individual item present in the Lists separately. Index value starts at 0 and end at n-1 where n is the list size.

For example, if a list stores 5 elements then index starts at 0 and ends with 4. To access or alter 1^st value use list_name[0] and to access or alter 5^th value then use list_name[4]. Lets see the example for better understanding:

x = [1, 2, 3, 4, 5, 6, 7, 8, 9]

# Positive Indexing
print(x[0])
print(x[4])
print(x[8])
print('=======\n')

# Negative Indexing
print(x[-2])
print(x[-4])
print(x[-8])

TIP: If you are using the Negative numbers as index then, Python will start looking for items from right to left

OUTPUT

Please use Negative numbers as index to access list items from right to left. I mean, access list items in reverse order.

# How to Access Python List Items
x = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']

# List Items using Positive Index
print("List Item at Index Position 0 = ", x[0])
print("List Item at Index Position 2 = ", x[2])
print("List Item at Index Position 4 = ", x[4])
print("List Item at Index Position 3 = ", x[3])
print('=======\n')

# List Items using Negative Index
print("List Item at Index Position -1 = ", x[-1])
print("List Item at Index Position -3 = ", x[-3])
print("List Item at Index Position -5 = ", x[-5])
print("List Item at Index Position -6 = ", x[-6])

OUTPUT

Iterate Python List items

The Python For Loop is the most common way to traverse the items in a list. Following statements will help us to iterate the list and print the items inside the list.

Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
for Fruit in Fruits:
    print(Fruit)

Above specified code will work fine to print items inside the list but, In order to alter the individual item we need the index position. To resolve this, we have to use the range function along with for loop as shown below

# Altering Python List using range
x = [1, 2, 3, 4, 5, 6, 7, 8, 9]

for Number in range(len(x)):
    x[Number] = x[Number] * 10
print(x)

Above specified code will multiply each and every item with 10. If you want to perform the calculation based on condition then, you can use Python If Statement inside the for loop
OUTPUT

In this example, we declared a string list.

First for loop used the for loop to iterate and prints the list items.
second for loop used the for loop along with range to iterate each and every list item using index positions.

Let me show you another example

# Iterate Python List Items

Fruits = ['apple', 'Mango', 'banana', 'orange', 'cherry','kiwi']

# Iterate List Items
for fruit in Fruits:
    print(fruit)

# Iterate List Items using Index 
for i in range(len(Fruits)):
    print("List Item at Index Position", i, " = ", Fruits[i])

OUTPUT

Insert items into Python List

Python provides the following options to insert new items into the existing list

Append(x): This method will help us to add item x at the end of the list.
Insert(i, x): This method will help us to insert the specified item x at index position i
Extend(New_List): This method will help us to add all the items in New_List at the end of the list

Fruits = ['Apple', 'Orange', 'Grape', 'Banana']

# Adding items using Python append
Fruits.append('Blackberry')
print(Fruits)

# inserting items using Python insert
Fruits.insert(2, 'Kiwi')
print(Fruits)

# Extending List using Python extend
Fruit_new = ['berry','Cherry']
Fruits.extend(Fruit_new) 
print(Fruits)

OUTPUT

Python List Slicing

In python Slice, the first integer value is the index position where the slicing will start and the second integer value is the index position where the slicing will end.

TIP: Slicing will go up to second integer value but will not include the value at this index position. For instance, if we specify list[1:4] then slicing will start at index position 1 and ends at index position 3 (not 4).

# Python List slicing

x = [1, 2, 3, 4, 5, 6, 7, 8, 9]

# Slicing the List using two indexes
a = x[2:6] 
print("Both Indexes = ", a)

# Slicing the List using First indexes
b = x[:6] 
print("No First Index = ", b)

# Slicing the List using Second indexes
c = x[2:] 
print("No Second Index = ", c)

# Slicing the List without using two indexes
d = x[:] 
print("No Indexes = ", d)

OUTPUT

Let me use the Negative numbers as the index values to slice the list items.

# Python List slicing

x = [1, 2, 3, 4, 5, 6, 7, 8, 9]

# Slicing the List using Negative indexes
e = x[-3:] 
print("Negative First Index = ", e)

# Slicing the List using Negative indexes
f = x[:-2] 
print("Negative Second Index = ", f)

# Slicing List using Negative indexes
g = x[-7:-2] 
print("Negative First and Second Index = ", g)

# Assigning new values to the List
x[1:3] = ['t','g']
print("After altering = ", x)

OUTPUT

From the above screenshot you can observe that,

If you omit the first index then, Slicing will start from the beginning
when you omit the second index then, Slicing will start from the first index and continue to the last
If you are using the Negative numbers as index then, Slicing starts from right to left

Remove Python List items

There are several ways to delete items from Python Lists:

Remove Python List items using remove() method

If we know the List item or the value inside the List then, we can use python remove() method to remove the list item.

# Removing Grape Item from Fruit List
Fruit1 = ['Apple', 'Orange', 'Grape', 'Banana']
Fruit1.remove('Grape')
print(Fruit1)
print('========')

# Removing Orange Item from Fruits List
Fruit2 = ['Apple', 'Orange', 'Grape', 'Banana', 'Orange']
Fruit2.remove('Orange')
print(Fruit2)
print('========')

# Removing Non Existing Grape Item from Fruits1 List
Fruit3 = ['Apple', 'Orange', 'Banana']
Fruit3.remove('Grape')
print(Fruit3)

OUTPUT

From the above screenshot you can observe that,

Within the First set of statements, We are removing the Grape item from the Fruit1 and displaying the remaining list.
In the Second set of statements, We are removing the Orange item from the Fruit2 and displaying the remaining list. If you observe closely, we have two Orange items in this list but remove() method removed only one item. This is because, remove() method will only remove the first instance of the item and ignores the remaining
Within the Third set of statements, We are removing the non existing item. That’s why it is throwing an error saying x is not in list

Removing Python List items using del statement

The Delete statement will remove the value at specified index and after deleting, remaining values will be moved up to fill the index gap. If we know the Index value or you want to delete range of items from the given List then, we can use python del statement to remove the list item.

# Delete Statement example in Python List
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']
del Fruits[1]
print(Fruits)
print('========')

del Fruits[1]
print(Fruits)
print('========')

del Fruits[1]
print(Fruits)
print('========')

del Fruits[1]
print(Fruits)

OUTPUT

From the above screenshot you can observe that,

Within the First set of statements, We are deleting the item at index position 1, which is Orange and displaying the remaining list. If you observe closely, after deleting the Orange, the index position of Grape become 1 and Banana as 2
In the Second set of statements, We are deleting the item at index position 1, which is Grape and displaying the remaining list.
Within the Fourth set of statements, We are removing the non existing item. That’s why it is throwing an error saying index out of range

Removing Python List items using pop() method

The pop() method will remove the value at specified index and display the removed element. After removing, remaining values will be moved up to fill the index gap. If we know the Index value and want to see the deleted value then, we can use python pop() to remove the list item.

# Pop Method example in Python List
Fruits = ['Apple', 'Orange', 'Grape', 'Banana']

Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')

Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')

Fruit = Fruits.pop(1)
print(Fruits)
print('Item extracted by Python Pop = ', Fruit)
print('========')

OUTPUT

Python List Methods

Following are the list of methods that are available to perform operations on python list:

Python list copy

List Copy() method help us to shallow copy the list items into completely new list

# Python List copy

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]

print("Original List : ", Fruits)
print("Original number List : ", numbers)

#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print("\nNew List : ", New_Fruits)

new_numbers = numbers.copy()
print("New Number List : ", new_numbers)

OUTPUT

Python list clear

List clear() method help you to clear all the existing list items. After executing this method, it returns empty list.

# Python List clear

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]

print("Original List : ", Fruits)
print("Original number List : ", numbers)

#Clear the List using Python Clear() Method
New_Fruits = Fruits.clear()
print("\nNew List : ", New_Fruits)

new_numbers = numbers.clear()
print("New Number List : ", new_numbers)

OUTPUT

Python list sort

List sort() method help you to sort the list items in Ascending order

# Python List sort

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]

print("Original List : ", Fruits)
print("Original number List : ", numbers)

#Sort the List using Python sort() Method
Fruits.sort()
print("\nSorted List : ", Fruits)

numbers.sort()
print("New Sorted Number List : ", numbers)

OUTPUT

Python list reverse

List reverse() method help you to reverse the items in a list

# Python List reverse

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]

print("Original List : ", Fruits)
print("Original number List : ", numbers)

#Reverse the List using Python reverse() Method
Fruits.reverse()
print("\nReverse List : ", Fruits)

numbers.reverse()
print("New Reverse Number List : ", numbers)

OUTPUT

Python list index

List index(x) function help you to return the index position of a user specified value in a list

# Python List index

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
numbers = [9, 4, -5, 0, 22, -1, 2, 14]

print("Original List : ", Fruits)
print("Original number List : ", numbers)

#Index of List items using Python index() Method
print('The Index position of Kiwi = ', Fruits.index('Kiwi'))
print('The Index position of Orange = ', Fruits.index('Orange'))
print('The Index position of Grape = ', Fruits.index('Grape'))

print('The Index position of 0 = ', numbers.index(0))
print('The Index position of 2 = ', numbers.index(2))
print('The Index position of -1 = ', numbers.index(-1))

OUTPUT

Python list count

List count(x) function help you to count the total number of times a specified value is repeated inside the list

# Python List count

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Apple', 'Kiwi']
numbers = [9, 4, -5, 0, 9, -1, 4, 9]

print("Original List : ", Fruits)

#Count of List items using Python count() Method
print('Number of Times Kiwi is repeated = ', Fruits.count('Kiwi'))
print('Number of Times Apple is repeated = ', Fruits.count('Apple'))
print('Number of Times Banana is repeated ', Fruits.count('Banana'))

print("\nOriginal number List : ", numbers)
print('Number of Times 9 is repeated = ', numbers.count(9))
print('Number of Times 4 is repeated = ', numbers.count(4))
print('Number of Times 0 is repeated = ', numbers.count(0))

OUTPUT

In the below program, we are applying all the list methods. This might help you to save the image to see all the functions.

Fruits = ['Apple', 'Orange', 'Banana', 'Kiwi', 'Grape', 'Blackberry']
x = [9, 4, -5, 0, 22, -1, 2, 14]

#Copying the List using Python Copy() Method
New_Fruits = Fruits.copy()
print(New_Fruits)

#Removing all the List items using Python Clear() Method
New_Fruits.clear()
print(New_Fruits)

# Sorting the List using Python Sort() Method
Fruits.sort()
x.sort()
print(Fruits)
print(x)

# Reverse the List using Python reverse() Method
Fruits.reverse()
x.reverse()
print(Fruits)
print(x)

# Index position of an item in the List using Python index() Method
print('The Index position of Banana = ', Fruits.index('Banana'))
print('The Index position of -1 = ', x.index(-1))

# Counting items in the List using Python count() Method
y = [9, 4, 1, 4, 9, -1, 2, 4]
print('Number of Times 4 is repeated = ', y.count(4))
print('Number of Times 9 is repeated = ', y.count(9))

OUTPUT

Python List sum

List sum function is to find the sum of all items available in a given lists

# Python List sum

int_list = [5, 10, 15, 20, 25]
print("List Items : ", int_list)
# sum of list elements
total = sum(int_list)

print("\nThe sum of total items in this list = ", total)

OUTPUT

Python List min

List min function is to used to find the minimum value among the given list items.

# Python List min

int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)

# Minimum list element
minimum = min(int_list)

print("\nThe Minimum item in this list = ", minimum)

OUTPUT

Python List max

List max function is to used to find the maximum value among the given list items

# Python List max

int_list = [50, 10, 150, 20, 205, 500, 7, 25, 175]
print("List Items : ", int_list)

# Maximum list element
maximum = max(int_list)

print("\nThe Maximum item in this list = ", maximum)

OUTPUT

Performing Arithmetic Operations on Python List

In this example we will show you, How to use Arithmetic Operators on Lists to perform arithmetic Operations.

# Python List count

x = [10, 20, 30, 40]
y = [15, 25, 35, 45]

# using + Operator
total = x + y
print("\nAddition : ", total)

# using * Operator
multi = x * 2
print("Multiplication : ", multi)

multi2 = y * 3
print("Multiplication of Y : ", multi2)

OUTPUT

From the above screenshot you can observe that,

+ operator is concatenating the python Lists
* operator is repeating the list for given number of times. Here it is three times